Whisk milk, egg substitute, oil and vanilla if using) in a small bowl until combined.

Coat a griddle or large nonstick skillet with cooking spray; heat over medium heat. Using 1/4 cup of batter for each pancake, cook 2 pancakes at a time until bubbles dot the surface, 2 to 3 minutes. Flip and continue cooking until browned, 1 to 2 minutes more. Repeat with the remaining batter.